Middle Winch

The middle winch onboard the "Margaret Mary". A winch is used deploying the nets and hauling them back to the vessel.  A vessel like the this which would fish two nets simultaneously normally has three. The middle winch is used to deploy the wires attached to the two nets in the centre of the arrangement.
It is also very well secured to the vessel as it is basically the anchor point for the net to the vessel. They are hydraulically driven and extremely powerful. The noise coming from the winch as the net is hauled up and the wire is forced along the drum by the mechanism at the back of the photo is deafening and really indicates how much force is on it.